I worked at a licence bureau in Ontario for 4 years, and had run into this question a lot. Unfortunately it isn't an easy thing. Technically if you are living in Canada as a perm resident, you are not allowed to drive a car you have registered in another province/state/country.
If you want to declare you were visiting Canada, and need to drive home to the States - you need to take your original registration into an office, with your driver's licence, and proof of insurance covering you to drive the vehicle (it can be temporary insurance) and you can apply for a temporary permit that would give you 15 days to drive it back to the States. Because Canada does not require yearly inspections on vehicles - OMIT that information altogether or you'll run into problems.
Now, if you plan on living in Canada perm, this is a bit more tricky. Did you declare at customs across the border that you were moving to Canada? If so - they would have given you a long form with a stamp on it. If you didn't tell them you were moving - then it's definitely a catch-22 because you need to get that paper, and in order to do so, need to take it back across the border into Canada. Honestly - the hassle and cost of importing a vehicle is HUGE - so you really should think about the cost of what it's worth to keep. You cannot sell a vehicle in Canada that you brought from the states, with a US title - so selling it is out of the question (as they new owner needs the long form as well to register it). You may only be able to sell it to a scrap yard unfortunately - as a lot of them do not register cars in their name.
Hope this helps somewhat? I can only speak for Ontario, as every province has vastly different rules. Best of luck!
Paige